During "happy hour" at the Summer Winter bar in Burlington, Mass., the bargain is on the bivalves, not the brews.

That's because Massachusetts legislators passed a law in 1984 banning bars from offering cut-price drinks. So James Flaherty, the bar's director of food and beverage, decided to use shellfish specials to draw customers.

"We've had to get creative by offering something other than a typical happy hour," he said. "Having a raw bar at the heart of the restaurant, we launched Oyster Happy Hour to appeal to the after work crowd with fresh, local selections and it's become a popular draw."

And Massachusetts isn't alone. The concept of happy hour — when bars offer lower prices or two-for-one specials — may seem like an American tradition, but is in fact illegal or restricted in quite a few places.

Laws vary by state, and even districts within states, so it's hard to get a handle on the national picture, but Ben Jenkins, vice president of government communications for the Distilled Spirits Council of the United States (DISCUS), has noted some recent activity aimed at updating happy hour laws.

A few states, including Oklahoma, Massachusetts and Virginia, recently have considered changes to existing restrictions. The bills failed, but are likely to re-emerge.

Meanwhile, happy hour became legal in Kansas last year after a 26-year ban. In 2011, Pennsylvania extended happy hour potentials from two to four hours and New Hampshire changed its law to allow establishments to advertise drinks specials.

DISCUS does not take a position on happy hour bills, but Jenkins sees the activity in the context of a larger modernization trend. "States across the country are updating their liquor laws to provide better consumer convenience and increased revenue without raising taxes," he says.

The patchwork nature of the laws is a holdover from Prohibition, when states were left to set regulations once the federal ban had been repealed. Some of the laws written then are still on the books, which can strike an anachronistic note today. For instance, it's still illegal to sell alcohol in South Carolina on Election Day. And it may surprise you to know that Moore County in Tennessee is "dry" and also home to the Jack Daniel Distillery.

The reasoning behind happy hour bans or restrictions generally stems from concerns that lowering prices will encourage high consumption and its ensuing problems.

"Some communities have issues of morality regarding promoting the drinking of alcohol or concerns regarding the kinds of behavior that can come from drinking too much," notes Kyle-Beth Hilfer, an advertising and marketing attorney with the New York-based law firm Collen IP.

Having so many different rules means bar owners and restaurateurs need to keep up with changes in the laws and read existing statutes carefully, says Hilfer.

Some states allow happy hours, but ban advertising them. Oregon, on the other hand, is OK with bars advertising general happy hours but not specific price discounts. Utah outlawed happy hours in 2011.

Advertising also can be tricky. A state may OK advertising happy hour specials, but going beyond the simple price and inviting customers to "lose weight at our low-carb beer happy hour," could be subject to regulation by state alcohol beverage officials, Hilfer explains. She recommends that proprietors of venues that serve alcohol and have happy hours have a lawyer vet advertising copy.

Social media has added a new twist to the mix. In Virginia, it's illegal for bars and restaurants to advertise happy hours in electronic media, radio, TV and the Internet, a law that goes back to 1984, long before Twitter had left the nest. This year, Virginia legislators considered changing the rules, though the bill ultimately was withdrawn, partly due to concerns about underage drinking.

This wasn't Virginia's first time to update old laws. In 2006, a tapas restaurant was cited for serving sangria because its recipe, a mix of red wine, brandy and fruit, violated a 1934 law prohibiting the mixing of wine or beer and spirits.